Conventionally, components of image-forming devices have been driven by AC power supplied from a commercial power supply. Japanese Patent Application Publication No. 2012-208450 describes a technology for controlling electricity conducted to a heater by switching a conduction signal at a timing based on the detection timing for zero-cross points in the outputted AC voltage. With this type of image-forming device, it is desirable to synchronize the timing at which the conduction signal is switched with the timing at which a zero-cross point is detected in order to reduce noise and power consumption.